The overall objective of this core is to generate, breed, genotype and provide genetically modified mice to investigators of the NWRCE. The unique resources developed and managed by this core and the increased needs and anticipated utilization of these resources motivated the creation of a separate transgenic mouse core for this competitive renewal. The Specific Aims of this core are: Aim 1) Advise investigators of the RCE on appropriate use of mouse models for their studies. Aim 2) Breeding, husbandry, and genotyping of existing mutant mouse lines and generation of new compound genetic mutants through intercrossing and genotyping of existing mutant mouse lines. Aim 3) Generation of new genetically modified mice. Aim 4) Rapid generation of congenic mice from mice on mixed genetic backgrounds using a 'speed congenics' approach.